Electrophotographic multicolor copy developed receptor employing solubilizable dyes

ABSTRACT

FOG-01 AN ELECTROPHOTOGRAPHIC PROCESS AND MATERIALS FOR THE PRODUCTION OF MULTI-COLOR COPIES OF A MULTI-COLOR ORGINAL IN WHICH AN ELECTROSTATIC CHARGE IS APPLIED TO A RECEPTOR SHEET HAVING A FACE PORTION SUBDIVIDED INTO PHOTOCONDUCTIVE SEGMENTS CONTAINING SENSITIZING COMPONENTS IN INTERSPERSED SEGMENTS WHICH COVER DIFFERENT PORTIONS OF THE VISIBLE LIGHT SPECTRUM AND IN WHICH EACH SUCH SEGMENT CONTAINS A SOLUBILIZABLE DYE COLOR CORRESPONDING TO THE COLOR OF THE SPECTRUM OTHER THAN THAT TO WHICH THE SEGMENT IS SENSITIZED AND IN WHICH THE EXPOSED RECEPTOR IS DEVELOPED WITH A TONER IN WHICH THE DYE COMPONENT IS SOLUBLE IN RESPONSE TO TONER ACTIVATION FOR TRANSFER OF DYE COLOR FROM THE DEVELOPED RECEPTOR TO COPY SHEETS BROUGHT INTO SURFACE CONTACT THEREWITH.

Feb. 20, 1973 F. 0. EACH ETAL ELECTROPHOTOGRAPHIC MULTIGOLOR COPYDEVELOPED RECEPTOR EMPLOYING SOLUBILIZABLE DYES Original Filed June 25,1969 FIG. Z

FIG, 4

Fire: 5

FIG. 6

United States Patent U.S. Cl. 96-15 11 Claims ABSTRACT OF THE DISCLOSUREAn electrophotographic process and materials for the production ofmulti-color copies of a multi-color original in which an electrostaticcharge is applied to a receptor sheet having a face portion subdividedinto photoconductive segments containing sensitizing components ininterspersed segments which cover diiferent portions of the visiblelight spectrum and in which each such segment contains a solubilizabledye color corresponding to the color of the spectrum other than that towhich the segment is sensitized and in which the exposed receptor isdeveloped with a toner in which the dye component is soluble in responseto toner activation for transfer of dye color from the developedreceptor to copy sheets brought into surface contact therewith.

This is a division of U.S. application Ser. No. 836,415, filed June 25,1969, now U.S. Pat. No. 3,630,729.

This invention relates to an electrophotographic process, materials andelements for the production of true color copies from multi-colororiginals with but a single exposure to light.

It is an object of this invention to provide a process for producingtrue color copies of multi-color originals by use of anelectrophotographic technique which requires but a single exposure tolight; which makes use of a single receptor sheet from which one or anumber of multicolor copies can be produced; in which the multi-colorcopy is produced by transfer from the receptor sheet to copy sheets fortrue color reproductions, and it is a related object to provide acomposition and elements for use in the practice of same.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is illustrated in theaccompanying drawings in which:

FIG. 1 is a top plan view of a portion of a receptor embodying thecoatings applied in accordance with a preferred practice of thisinvention;

FIG. 2 is an enlarged sectional view through a portion of the receptorsheet shown in FIG. 1;

FIG. 3 is a schematic sectional view similar to that of FIG. 2,illustrating the conditions existing in response to exposure to amulti-color original;

FIG. 4 is a schematic sectional view of the exposed receptor of FIG, 3after treatment with a developer composition;

FIG. 5 is a schematic diagram showing the transfer of the multi-colorimage from the receptor to a copy sheet; and

FIG. 6 is a top plan view of the multi-color copy produced from theexposed receptor of FIG. 5.

Briefly described, the concepts of this invention are practiced with areceptor provided with a number of photoconductive coatings each ofwhich is formulated to contain (1) an organic insulating binder, such asan organo- Patented Feb. 20, 1973 silicon resin, a butadiene-styrenecopolymer resin, a modified alkyd resin and the like; (2) aphotoconductor such as photoconductive zinc oxide or otherphotoconductive material such as described in the Middleton et al. Pat.No. 3,121,006; (3) a sensitizing component, such as a sensitizing dyewhich sensitizes the photoconductor to light of a selected wave lengthwithin the visible light spectrum while reflecting wave lengths outsidesaid range, with each coating containing a sensitizing ingredient whichsensitizes the photoconductive coating to a dilferent portion of thevisible light range, whereby the total of the coating providessensitivity which covers the entire visible light range, and (4) asoluble dye component in each coating having a color transfer valuecorresponding to the subtractive color for which the particular coatingis sensitized, as represented by a color produced by the combination ofranges of light reflected by the sensitized photoconductor of theparticular coating composition and in which the concepts of thisinvention include the use of a developer which is formulated with acomponent, normally identified as a toner, which comprises a solidmaterial in finely divided form which, in response to activation as byheat, solvent, vapors or the like, functions as a solvent for thesoluble dye component (4) of the photoconductive coating to effecttransfer of the dye color from the portions of the coating immediatelyunderlying the activated solvent for transfer to copy sheets pressedinto surface contact with the receptor to produce true color copies ofmulti-color originals in response to a single exposure.

By way of illustration, the visible spectrum may be subdivided intocontiguous segments, preferably three or more segments, such assubdivision of the visible light spectrum, assumed to be included withinthe range of 400-700 am, into segments of about 400-500, 500-600 and600-700 nm. The sensitizing component for one coating would then beselected to sensitize the photoconductor to light of within the range of400-500 nm. (blue sensitivity) and to reflect light within the range of500-700 nm. This particular effect can be achieved by the use of adyestuff corresponding to the yellow layer in the well knownphotographic color processes based upon the subtractive tri-pack, suchas Auramine 0 (Cl. 41,000). The soluble dye component formulated intothe described coating composition is selected of a dyestutf having ayellow color or a color which represents the combination of thereflected light range of 500-700 nm.

Another or second coating is formulated with a sensitizing componenteffective to sensitize the photoconductor in the light range of 500-600nm. (green sensitivity), while reflecting light within the range of400-500 nm. and 600-700 nm. This can be achieved by the use of a magentacoating, when reference is made to the subtracti ve tri-pack system,such as by formulating the coating composition to contain acridine red(C.l. 45,000). The soluble dye component formulated into the describedcoating would be selected of a dyestuff having preferably a blue-redcolor corresponding to the combination of the reflected light within therange of 400-500 and 600- 700 nm.

The third coating would be formulated to contain a sensitizing componentwhich sensitizes the photoconductor to absorbed light within the rangeof 600-700 nm. (red sensitivity), while reflecting light within therange of 400-600 nm. This can be achieved by a cyan coat, such as withPatent Blue (C.I. 42,045). The soluble dye component in the thirdcoating would be selected of a dyestuff giving a blue-green colorcorresponding to the range of reflected light or the combination ofcolors within the range of 400-600 nm.

When based upon the amount of photoconductive zinc oxide, the describedcoating compositions can be formulated to contain the resinous binder inan amount within the range of 10-40 parts by weight of resinous binderper 100 parts by weight of zinc oxide, and preferably in an amountwithin the range of 15-30 parts by weight of resinous binder per 100parts by weight of zinc oxide. The sensitizing component or dyestuif isformulated in the coating composition in an amount within the range of0.001 to 5.0 part by weight per 100 parts by weight zinc oxide andpreferably within the range of 0.01 to 2.5 part by weight per 100 partsby weight of zinc oxide, the amount depending somewhat upon thesensitizing dye, such as 0.13% by weight magenta color, as in the formof acridine red having a spectral response in the range of 495-620 A.,0.06% of the cyan color, as represented by Patent Blue having a spectralresponse in the range of 600700 A. and 1.2% by weight of the yellowcolor as represented by Auramine having a spectral response within therange of 405-500 A. It will be understood that, except for cost, morethan .0 parts by weight of sensitizer per 100 parts by weight zinc oxidecan be used. The soluble dye component can be formulated into eachcoating in an amount within the range of 0.5-20.0 parts by weight per100 parts by weight of zinc oxide and preferably in an amount within therange of 1-5 parts by weight per 100 parts by weight of zinc oxide. Theforegoing amounts of sensitizer and soluble dye components specified inparts by weight may be taken as corresponding to the percent by weightof the photoconductive coatings formulated of photoconductive zinc oxideor a photoconductor other than zinc oxide, but in which the percentageis adjusted by the weight ratio of zinc oxide to said otherphotoconductive material in the coating.

The soluble dye component is preferably formulated in the respectivecoating compositions as a dispersed dye but it will be understood thatthe soluble dye component can be incorporated in other states.

The coatings are produced from compositions containing the describedcomponents in combination with a diluent which is a solvent for theresinous binder and ap plication may be made to the substrate in coatingweights, when formulated of a zinc oxide photoconductor, within therange of 8-40 pounds per 3,000 square feet of surface area, andpreferably within the range of -30 pounds per 3,000 square feet ofsurface area.

The separate coating compositions are applied or otherwise imprinted onthe surface of the substrate in various patterns. The essentialrequirement is that the face of the coated substrate define a finalpattern of separate, small light responsive areas of each coatinginterspersed one with another substantially uniformly over the surfaceof the substrate in closely spaced relation.

This can be accomplished by application of the separate coatingcompositions in a pattern of dots, circles, beads, spheres, squares,lines or the like configurations. Since it is not essential that theseparate light responsive areas be arranged coplanar, it is preferred toapply the coating compositions either in the form of lines whichcriss-cross one another over the surface of the substrate or morepreferably to apply one coating composition as a continuous coating overthe surface of the substrate and to apply the remaining coatings aslines which criss-cross over the underlying base coat as islands or dotsof various configuration which overlie the base coat. Thus the receptorsheet will be formed of a substrate having portions coated with only onelayer of the first coating, other portions with two layers formed of thefirst and second coats and first and third coats; and still otherportions formed of three layers of the first, second and third coating,etc.

Having described the basic concepts of the invention from the standpointof compositions and construction of the elements employed, illustrationwill now be made by way of examples which represent the practice of theinvention and in the utilization thereof in carrying out the new andnovel process for multi-color reproduction of multi-color originals bythe electrophotographic technique. The description will hereinafter bemade with respect to a system of compositions based upon thesubstractive tripack, but it will be understood that the visible lightspectrum can be otherwise divided for the selection of componentidentified as the sensitizing component and corresponding soluble dyecomponent embodied in each of the separate coating formulations.

EXAMPLE 1 Magenta coating composition: (green sensitive):

100 grams photoconductive zinc oxide (Photox New Jersey Zinc Company) 25grams modified alkyd resin (DeSoto E-l04-13A DeSoto Chemical Coatings,Inc.)

0.13 gram sensitizing dyeAcridine RedC.I. 45,000

(Allied Chemical Corp.)

1.5 grams dispersed dyespirit soluble Fast Red 33 (Allied ChemicalCorp.)

60 ml. toluene EXAMPLE 2 Yellow coating composition (blue sensitive):

grams photoconductive zinc oxide (Photox 80) 25 grams modified alkydresin (DeSoto E-104-13A) 0.05 gram sensitizing dyeAuramine OC.I. 41,000

(Allied Chemical Corp.)

1.5 grams dispersed dyeCalcofast Spirit Yellow TG (American CyanamidCompany) 60 ml. solvent-toluene EXAMPLE 3 Cyan coating composition (redsensitive):

100 grams photoconductive zinc oxide (Photox 80) 25 grams modified alkydresin (DeSoto E-104-13A) 0.05 gram sensitizing dyePateut BlueC.I. 42,045

(Allied Chemical Corp.)

1.5 grams dispersed dyespirit soluble Fast Blue 66 (Allied ChemicalCorp.)

60 ml. solvent-toluene In each of the examples, the resinous binder,zinc oxide and solvent are first blended together by mixing for aboutfive minutes. The sensitizing dye, in solution in methanol, is added andblended by mixing for about one minute. The dispersed dye is finallyadded and blended with mixing for about one to two minutes.

The first coating 20, which may be the magenta coat of Example 1, isapplied either by a roller coater, by a metering rod, or by handdraw-down a wire wound rod, onto Weyerhauser Base A paper 10 in acoating weight of about 20 pounds per 3,000 square feet, and then dried.The yellow coating composition of Example 2 is applied, as by silkscreen, in a coating weight of about 15 pounds per 3,000 square feet ofsurface area in a pattern of closely spaced parallel lines 22 whichextend crosswise over the surface of the first coating 20. It will beunderstood that the described coatings can be applied in various othersequences such as a first coating of the yellow coat of Example 2followed by second and third coatings of Examples 1 and 3, or a firstcoat of Example 3 and second and third coatings of Examples 3 and 2 or 2and 3, etc.

The cyan coating composition of Example 3 is also applied, as by silkscreen, in a coating weight of about 15 pounds per 3,000 square feet ofsurface area in a pattern of closely spaced parallel lines 24 whichextend lengthwise over the first and second coatings to providecross-over points 26 having three thicknesses of coating with the thirdcoating 24 uppermost on the face of the substrate or paper base sheet.

The final coated sheet constitutes a receptor suitable for use in thepractice of this invention with separate sections 28 having a singlecoating thickness of the magenta coating, separate sections 3 having adouble coating thickness formed of a lowermost magenta coating 20 and anuppermost yellow coating 22 and a lowermost magenta coating 20 and anuppermost cyan coating 24 and still other sections 32 having a triplecoating thickness formed of a lowermost magenta coating 20, anintermediate yello-w coating 22 and an uppermost cyan coating 24. Thusthe exposed face of the receptor presents separate sections of each ofthe coatings in substantially uniformly dispersed relation over the faceof the receptor sheet.

The receptor sheet is charged in the usual manner, now well known to theelectrostatic copy art, as by subjecting the face of the receptor to acorona spray as it is exposed to corona discharge from wires operatingat a potential of about 6000 to 8000 volts. The charged wires, whichextend across the face of the receptor, are either transported over theface of the receptor or the receptor is displaced beneath the wires. Theelectrostatic charge is deposited over the entire receptor covered byone or more of the photoconductive coatings.

The charged receptor is next exposed to the multicolor original. Suchportions of the original which are blue in color, for example, willcause discharge of the corresponding areas on the face of the receptorformed of the yellow coating which is sensitized to blue, leaving thecharges in the corresponding areas on the exposed face sections of themagenta and cyan coatings for subsequent development.

The portions of the original which are green in color cause discharge ofthe corresponding areas 28 on the face of the receptor formed of themagenta coating, which are sensitized to green, leaving the charge 34 onthe corresponding areas on the face sections 32 of cyan and sections 30of yellow coating for subsequent development, as depicted in FIG. 3.

Similarly, the portions of the original which have the color red willcause discharge in the corresponding areas of the receptor of the cyansections 32 on the exposed face of the receptor sheet which aresensitized to red, leaving the charges on the corresponding areas in theexposed face sections of magenta and yellow for subsequent development.

The exposed receptor sheet is developed in the conventional mannereither with a dry powder developer or with a liquid developer, but inwhich the conventional particles of toner in the dry powder developersuspended in the liquid developer are substituted by finely dividedparticles of a compound which, when activated as by heat or solvent,vapor and the like, becomes a solvent for the dispersed dye in thecoating.

The following examples are given by way of illustration, but not by wayof limitation, of liquid developing compositions embodying the featuresof this invention.

EXAMPLE 4 5.0 grams toner (Antipyrine) 400 ml. liquid carrier (IsoparGHumble Oil Co.) 5 grams charge director (Fuel Oil Additive #2DuPont)EXAMPLE 5 5.0 grams toner (l-allyl-Z-thiourea) 400 ml. liquid carrier 5grams charge director The Isopar G used as the liquid carrier in theabove example is a paraffinic hydrocarbon liquid having 11.8% Chydrocarbons, 56.2% C hydrocarbons, 31.7% C hydrocarbons, less than .3aromatics and less than .1 olefins, a boiling point within the range of3l8350 F., a flash point of 104 F. and a specific gravity of 0.748.Other liquid carriers used in liquid developers may be used as long asthe toner compound is not dissolved therein. The Fuel Oil Additive #2 isa solution of a methacrylate copolymer having an average molecularweight of 50,000. Again, other conventional charge directors can beemployed.

The antipyrine of Example 4 and the l-allyl-Z-thiourea 6 of Example 5are merely representative of suitable toner particles which may be usedfor development of the latent electrostatic image of the chargedsections that remain after exposure. Other toner particles may be usedwhich meet the requirements:

(1) a solvent for the soluble dye component in the coatings when thetoner is in a molten or activated state; (2) capable of being reduced toa finely divided form in which it is retained in the liquid or powdereddeveloper composition;

(3) capable of taking on a charge, such as a positive charge when usedwith a charged photoconductive coating of zinc oxide;

(4) suitably located within the triboelectric series to produce thedesirable charge development.

Representative of other suitable compounds which meet these requirementsand can be used as toners are vanillin. 1,6-hexanediol, 1,10-decanediol,ethyl urea, acetamide, benzohydrol, 2,2-dimethyl-l, 3-propanediol,ammonium acetate, ammonium formate and pyrazine. The toner particles canbe employed in various concentrations in the developer composition, suchas within the range of 2-20% by weight, and preferably 3-l0% by weight,in a dry powder developer and within the range of 0.220% by weight andpreferably 2-10% by weight in a liquid developer. When use is made of adry powdered developer which is applied by brushing or the like, thetoner concentration can range up to percent by weight toner in thedeveloper.

Continuing with the development process, in response to the applicationof the developer composition, toner particles 36 will be retained on theportions on the face of the receptor which remain charged to define thelatent electrostatic image after exposure while the discharge sectionson the face of the receptor will remain substantially free of the tonerparticles, as depicted in FIG. 4.

Thereafter the developer receptor sheet is pressed into surface contactwith a copy sheet 40, as by passage of the composite assembly betweencompression rollers heated to a temperature above the melting pointtem-- perature for the toner, such as at a temperature above 1l1l13 C.which is the melting point for antipyrine, or above a temperature of7778 C. which is the melting point for 1-allyl-2-thiourea, andpreferably by heating the toner particles to a temperature which exceedstheir melting point by a slight amount preferably about 5-10 F. As aresult, the toner particles are reduced to a fluidized state to enablesolution of the dispersed dye in the underlying portions of thephotoconductive coating in the face of the receptor for transfer of thecorresponding dye color, as by diffusion, from the receptor to the copysheet 40.

In the example illustrated in FIGS. 4 and 5, the cyan and yellowcoatings 32 and 30, respectively, which remain charged and retain thetoner particles 34 on development, solubilize the Calcofast SpiritYellow TG and the Spirit Soluble Fast Blue 6G to cause transfer to thecopy sheet with resultant reproduction 50 of the green color of theoriginal. In such areas of the original which are black, such as theprinted areas, none of the sections in the face of the coated receptorwould become discharged upon exposure. As a result, each of the areasaccept toner for transfer of dyestuffs from all of the three basic colorsections which together appear black in the copy sheet.

It will be apparent that the copy produced by the combination of colorstransferred from the developed receptor sheet will correspond to thecolored original and that the developed receptor can function in amanner of a spirit master to produce multiple copies of the multi-colororiginal, as by the successive passage of copy sheets into pressurecontact with the developed receptor until the soluble dyestutf in thetoned face segments are exhausted.

It will be apparent from the foregoing that I have provided a new andnovel electrophotographic process for the production of true colorcopies of multi-color originals by the use of but a single exposure forthe development of a master from which one or more multi-colored copiescan be produced.

It will be understood that changes may be made in the details offormulations, application and process steps, without departing from thespirit of the invention, especially as defined in the following claims.

We claim:

1. A developed receptor for electrophotographic production ofmulti-color copies of a multi-color original comprising a conductivesubstrate in the form of a sheet and two or more photoconductivesections interspersed on the face of the substrate, each sectioncontaining a photoconductive component and each different sectioncontaining a sensitizing component for sensitizing the photoconductor toa segment of the visible light range for absorption of light within saidrange and reflection of light outside said range, and a dye colorcomponent which corresponds to the color of the reflected range oflight, with the sensitizing component in one section dilfering from thesensitizing component in other sections to cover substantially theentire visible light range, and toner particles electrostaticallyattracted to sections of the receptor which have retained a latentelectrostatic image in response to exposure to an original whereby thetoner particles are attracted to sections of the receptor in areas ofthe receptor corresponding to areas of the original having the samecolor as the dye color component of the sections, said toner particlesbeing formed of a material which, when in activated state, serves as asolvent for the dye color component.

2. A receptor sheet as claimed in claim 1 in which the photoconductivecomponent comprises photoconductive zinc oxide.

3. A receptor sheet as claimed in claim 1 in which the sensitizingcomponent is a sensitizing dye.

4. A receptor sheet as claimed in claim 3 in which the sensitizing dyeis present in an amount within the range of 0.001 to 5.0 percent byweight per 100 parts by weight of the photoconductive component whenthat photoconductive component is zinc oxide.

5. A receptor sheet as claimed in claim 1 in which the golor dyecorrespoding to the reflected light is a dispersed 6. A receptor sheetas claimed in claim 5 in which the dispersed dye is a spirit solubledye.

7. A receptor sheet as claimed in claim 5 in which the soluble dyecomponent is present in an amount within the range of 0.5 to 20 percentby weight per parts by weight of the photoconductive component when thatphotoconductive component is zinc oxide.

8. A receptor sheet as claimed in claim 1 in which the separate sectionsare selected of three difierent compositions with each of thecompositions containing a separate member of the subtractive tri-packcolors of magenta, cyan and yellow.

9. A receptor sheet as claimed in claim 1 in which the sections areformed in a pattern of criss crossing lines of the diflerentcompositions.

10. A receptor sheet as claimed in claim 1 in which the sections areformed of a pattern of separate islands of the different compositions.

11. A receptor sheet as claimed in claim 1 in which the sections on thesubstrate comprise a coating of one composition extending over thesurface of the substrate with the other compositions arranged incriss-cross pattern of lines over the surface of the coating.

References Cited UNITED STATES PATENTS 3,212,887 10/1965 Miller et al961.2 X 3,329,590 7/1967 Renfrow 961.2 X 2,940,847 6/1960 Kaprelian96l.2 X 3,147,699 9/ 1964 Land 96l.2 X 2,962,374 11/1960 Dessauer 961.2X 3,549,359 12/1970 Honjo et al. 961.2 3,556,783 1/ 1971 Kyriakakis96l.2

GEORGE F. LESMES, Primary Examiner J. R. MILLER, Assistant Examiner U.S.C1. X.R.

